PTCO 2KRO 1702A 2K ePROM

Here is a dump extracted from three 1702-A ePROMs installed in a PTCO 2KRO board.

The dump below consists of the three 1702-A ROMs. The first is (my guess) some sort of 8080 monitor program or bootstrap, the second is the PTCO VDM-1 board initialization routine, and the third may be additional instructions for a 3P+S card to interface to run with a teletype (ASR33?). Just a guess. I will update the thread after I get a chance to test. I also have to determine the memory locations of each. The card is not documented on the web. The jumper W is in the "1" position. I am guessing 1 = C000, 2 = D000, 3=E000, 4=F000 - I will update this thread after I run some tests.

I installed this S-100 board into my IMSAI 8080 to see if I can read the ePROMs from the front panel having already verified the chips are OK (see also 1702A repair below). I have no manual for this board (have one?).

A little experimentation revealed how to assign the page address using jumpers 11-15. In the photo above, note how jumper 15 is set to the top jumper (or "high") post and the rest are connected to the "low" posts. This combination sets the starting page address of the board to 80H (8000 0000 Hex). When I change jumper set 15 to the low post, starting page address becomes 0000 0000 Hex.

The wait state jumper posts read W and 1-4. The photo shows how the jumper is set to connect to jumper 1, indicating no wait state needed (I believe).

This photo shows a 256 byte 1702A ePROM with a broken pin, since repaired (note silver-colored pin 2nd from right). The ePROM repair was a success, but given its fragile state I replaced from use and installed a newer 1702A onto the ePROM board, see photo above. Fortunately I had an image of the ePROM and was able to make a replacement chip. Click for larger View.